Gas filled vertical dynamoelectric machine

ABSTRACT

A totally enclosed, inert gas filled vertical dynamoelectric machine is described wherein liquid lubricant in the lower bearing housing is employed to seal the machine output shaft against the loss of inert gas. To inhibit loss of lubricant from the seal, a stationary oil sleeve concentrically disposed within a zone between the rotor shaft and shaft sleeve protrudes to a height in excess of the oil level within the housing by an amount at least equal to the change in level produced by the pressure of the inert gas within the machine. The lower bearing preferably is enclosed by a selectively notched bearing cover which serves in conjunction with annular grooves upon the shaft sleeve to prevent oil creepage along the exterior of the shaft while blow-out of oil from the seal by excessive gas pressure within the machine is inhibited by a liquid filled, generally U-shaped tube communicating the motor interior with the ambient. To prevent turbulence produced by rotation of the rotor from breaking the seal, the lubricant should extend to a level above the bearing or a selectively apertured partition could be inserted between the lower end of the shaft sleeve and the bearing.

United States Patent 1 Gleichman GAS FILLED VERTICAL DYNAMOELECTRICMACHINE Robert F. Gleichman, San Jose, Calif.

General Electric Company, Schenectady, NY.

[22] Filed: Apr. 25, 1972 211 Appl.No.:247,369

[75 Inventor:

[73] Assignee:

[52] U.S. Cl 3111/90, 310/58, 310/157, 184/6 [51] Int. Cl. ..1-102k 5/16[58] Field of Search 310/157, 91, 58, 310/55, 61,90; 308/134.1; 184/6[56] References Cited UNITED STATES PATENTS 3,158,768 11/1964 Schonwald310/157 3,083,312 3/1963 Moore 310/157 2,610,992 9/1952 Johns 310/612,635,198 4/1953 Wieseman 310/157 FOREIGN PATENTS OR APPLlCATlONS751,421 9/1933 France 310/157 Primary Examiner-R. Skudy Atl0rney-Va1e P.Myles et a1.

[57] ABSTRACT A totally enclosed, inert gas filled verticaldynamoelectric machine is described wherein liquid lubricant in thelower bearing housing is employed to seal the machine output shaftagainst the loss of inert gas. To inhibit loss of lubricant from theseal, a stationary oil sleeve concentrically disposed within a zonebetween the rotor shaft and shaft sleeve protrudes to a height in excessof the oil level within the housing by an amount at least equal to thechange in level produced by the pressure of the inert gas within themachine. The lower bearing preferably is enclosed by a selectivelynotched bearing cover which serves in conjunction with annular groovesupon the shaft sleeve to prevent oil creepage along the exterior of theshaft while blow out of oil from the sea] by excessive gas pressurewithin the machine is inhibited by a liquid filled, generally U-shapedtube communicating the motor interior with the ambient. To preventturbulence produced by rotation of the rotor from breaking the seal, thelubricant should extend to a level above the bearing or a selectivelyapertured partition could be inserted between the lower end of the shaftsleeve and the bearing.

12 Claims, 4 Drawing Figures PAIliNIEnAus mu sum 2 or 3 FIG. 2.

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FIG. 3

GAS FILLED VERTICAL DYNAMOELECTRIC MACHINE This invention relates toinert gas filled vertical dynamoelectric machines and, in particular, toa vertical dynamoelectric machine having a novel lower seal to inhibitloss of pressurized inert gas from the machine.

When a dynamoelectric machine is to be operated in a potentiallyexplosive environment, e.g., a sewage treatment plant wherein gases suchas hydrogen may be generated, the machine often is charged with an inertgas to prevent leakage of the explosive atmosphere into the machine.Because the machine shaft normally must be brought through the machinehousing for coupling to the driven equipment, complete enclosure of thehousing is difficult to achieve and the end shields for inert gas filleddynamoelectric machines in explosive environments typically are designedto permit controlled leakage of the inert gas from the machine at theseal.

Among the seals typically utilized to contain pressurized inert gaswithin a horizontal motor are forced lubrication bearing and shaft sealswherein sealing oil is fed through dual entrances into an axiallypartitioned split sleeve bearing with the oil from the bearing sealbeing fed to a compartmentalized gas separating chamber wherein gasbubbles within the oil are removed prior to recirculation of the oilthrough the seal. Proposals also have been made that labyrinth typeseals of various design be utilized to allow controlled leakage of gasfrom the motor or that contacting face seals (e.g., of a design such asis shown in McHugh U.S. Pat. No. 3,704,019, issued Nov. 28, l972, whichis assigned to the assignee of the present invention) be utilized forsuch purpose.

I have discovered, however, that the liquid lubricant for the shaftbearing can be employed to seal a vertical machine by utilizing anelongated lubricant sleeve between the rotor shaft and shaft sleeve toaccommodate the excessive lubricant elevation produced by the pressureof the inert gas upon the lubricant. While arrangements of this generalnature heretofore have been utilized with non-pressurized verticalmotors to retain the lubricant (e.g., a structure of somewhat similardesign is described in Tillma patent application, Ser. No. 73,767, filedSept. 21, 1970, to retain bearing lubricant in a non-pressurizedvertical motor), the lubricant sleeves of these prior art arrangementsextend only slightly above, e.g., approximately one to two inches above,the level in the lower bearing lubricant reservoir dependent upon suchfactors as the size of the motor and the amount of agitation produced byrotation of the shaft sleeve. The oil sleeve of the present invention,however, extends above the oil level in the bearing reservoir by anadditional amount at least equal to the change in level produced by theinert gas pressure in the machine to seal the machine and to inhibitleakage of oil at the shaft.

Should the pressure of the inert gas within the machine increase beyonda limited range during operation, oil within the lower bearing could beexpelled from the machine leading to bearing failure. I also havediscovered that a liquid filled trap can serve within the machine as apressure release valve to limit excessive pressures before lubricant isexhausted from the seal.

It is therefore an object of this invention to provide a novel inert gasfilled vertical motor having a superior seal.

It is also an object of this invention to provide a gas filled verticalmotor having a novel pressure release valve to inhibit exhaust oflubricant from the lower seal.

These and other objects of this invention generally are achieved by thedisposition of an elongated lubricant sleeve between the rotor shaft andthe shaft sleeve to accommodate the excessive lubricant levels producedby the pressurized inert gas upon the seal. Thus, a dynamoelectricmachine in accordance with this invention typically would include aconventional rotor and stator along with suitable means, such as rotormounted fans, for circulating a pressurized gas through the machine toremove heat therefrom by forced convection and conduction to a coolersurface. Lubricant within the lower bearing of the machine is employedto inhibit leakage of pressurized gas from the machine, and the shaftseal is characterized by a rotary sleeve circumferentially disposedabout the lower end of the shaft with a lubricant sleeve extendingconcentrically into the zone between the shaft and shaft sleeve toconfine liquid lubricant for the lower bearing within the machine. Inaccordance with the teachings of this invention, the lubricant sleeveextends to a height above the liquid lubricant level within the bearingby an amount at least equal to the change in level produced by thepressure of the inert gas within the machine to inhibit spillage of thelubricant over the oil sleeve. Means also are provided, such as ananormally high level of lubricant within the bearing or a selectivelyapertured partition beneath the bearing, to prevent agitation producedby rotation of the bearing from breaching the gas seal.

Although this invention is described with particularity in the appendedclaims, a more complete understanding of the invention may be obtainedfrom the following detailed description ofa specific embodiment of theinvention when taken in accordance with the appended drawings wherein:

FIG. 1 is a sectional view of a vertical motor having a lower shaft sealin accordance with this invention,

FIG. 2 is an enlarged sectional view of the lower shaft seal of themotor illustrated in FIG. 1,

FIG. 3 is an enlarged view of a pressure release valve employed in thegas filled motor to inhibit loss of lubricant from the lower bearinghousing, and

FIG. 4 is an alternate seal configuration in accordance with thisinvention permitting conventional levels of lubricant in the lowerbearing.

An inert gas filled vertical motor 10 in accordance with this inventionis illustrated in FIG. 1 and generally includes a stator 12circumferentially disposed about a rotor 14 mounted upon verticallyextending shaft 16. The motor is enclosed within a sealed housing 18with heat generated by current flow through the motor being removed bycirculating a pressurized inert gas, such as nitrogen, between the coilsof heat exchange unit 20 mounted along one side of the motor withinhousing 18. The drive end of shaft 16 extends from the lower end of thehousing to be connected to a load (not shown) and loss of inert gas fromthe motor in accordance with this invention is inhibited by a lowerbearing seal 22.

Other than the lower bearing seal (and other features relative to theseal protection to be more fully explained hereinafter), motor generallyis conventional in design with the lower end of shaft 16 being rotatablymounted within a guide bearing 24 while a spherical roller thrustbearing 26 at the upper end of the shaft serves both as a guide bearingand as a thrust bearing to permit rotation of shaft 16 while supportingthe weight of the rotor and the externally applied axial thrust loadwithin the structure. Bearings to accomplish the foregoing purposes arewell-known in the art with thrust and guide bearings suitable for thisinvention being disclosed in the aforementioned Tillma patentapplication. It will be appreciated, however, that this invention alsois applicable to machines having other type bearings, e.g., the machinecould have combinations of ball thrust bearings, plate-type thrustbearings,

ball lower guide bearings and sleeve type upper and lower guidebearings. If desired, an anti-reverse device (not shown) of knownconfiguration also could be mounted upon the shaft to prevent reverserotation of the rotor.

Cooling of motor 10 in accordance with this invention is accomplished bycirculating the pressurized inert gas through the motor housing by fans30 mounted at opposite ends of rotor 14. As is illustrated by the arrowsdepicting gas flow within the machine, gas passes axially inward fromboth ends of the rotor to aligned radial passages 32 in the rotor andstator to absorb heat therefrom before flowing between the coils of heatexchange unit wherein a fluid, typically water, is circulated to coolthe pressurized inert gas by forced convection and conduction. Thecooled gas then is divided in axially opposite streams by motor housing18 and suitable baffles 36 direct the streams to the fans at oppositeends of the rotor for recirculation through the machine-To inhibit entryof an explosive gas into the motor, the inert gas within motor 10typically is pressurized to a pressure of approximately 2 inches water,i.e., 0.147 inches H to assure an outflow of inert gas through anyminute opening in the housing.

In accordance with this invention, the lower end of shaft 16 is sealedutilizing the lubricant, typically oil 38, within lower guide bearing'24as is illustrated in FIG. 2. The oil for the guide bearing preferably isretained within a first annular oil channel 40 of limited capacity incommunication with guide bearing 24 while a large capacity, externallyfed, oil storage reservoir 42 is communicated to oil channel 40 througha selectively dimensioned aperture 44 to supply limited quantities offresh oil to the bearing as needed. An elongated oil sleeve 46 extendingconcentrically into the annular zone 48 formed between shaft 16 andshaft sleeve 50 serves to confine the oil within the lower guidebearing. In accordance with this invention, the oil sleeve extends to aheight substantially greater than prior art oil sleeves of similardesign, i.e., oil sleeve 46 extends to a height greater than the heightof the lubricant in bearing 24 by an amount at least equal to theadditional oil level height produced by the inert gas pressure withinthe motor. Thus, when the height of the oil within the bearing isapproximately X inches and the pressure of the inert gas within themotor is Y inches of water, oil sleeve 46 should extend to a height inexcess of X Y (DZ/Di) wherein D1 and D2 are the densities of the oilwithin the lower bearing and water, respectively. In general,

oil sleeve 46 should extend at least three inches beyond the height ofthe oil within oil channel 40 (as opposed to protrusions ofapproximately 1 to 2 inches for prior art vertical motor seals utilizedin non-pressurized motors). A rapid appraisal of the desired height ofoil sleeve 46 for a given pressurized motor may be obtained by addingthe oil level sustained by the gas pressure in the motor (plus a givenpercentage, e.g., 50% of the substained oil level as a safety factor) tothe conventional height of the oil sleeve for a non-pressurized motor ofcomparable design.

As is shown more clearly in FIG. 2, radially inner ring 52 of guidebearing 24 is fixedly secured between a shoulder 54 in shaft sleeve 50and lockwasher 56 upon tightening of ball bearing nut 58 while radiallyouter ring 60 of the guide bearing is juxtaposed with an annualrprotrusion 62 in the motor end shield. The lower bearing seal isenclosed by annular bearing cover 64 secured in fixed position by capscrews 66 to confine oil thrown by the guide bearing during operation.To inhibit flow of oil along the outer periphery of shaft sleeve 50, aplurality of annular notches 72 are provided along the exterior surfaceof the sleeve to coagulate the upwardly traveling oil film into dropletswhereafter centrifugal force throws the droplets into grooves 74 inbearing cover 64. The lubricant then flows down through exit channels 76in the bearing cover to return to oil channel 40 or oil storagereservoir 42.

The height of the oil level within the guide bearing has been found tobe highly important for the proper operation of this invention. For aseal of the design illustrated in FIGS. 1 and 2 with conventionallyutilized lubricant levels, i.e., with the oil extending only to theheight of the upper edges of the raceways in guide bearing 24 (shown bydotted line 68), a leakage rate of approximately 14 cubic feet per hourwas observed in a 440 rpm motor notwithstanding an inert gas leakagerate of only 1 cubic foot per hour during non-operating periods. Theexcessive leakage rate of the inert gas during operation is postulatedas being caused by breach of the seal resulting from turbulence in theoil in the region 40 below the bearing produced by rotation of the ballbearing. When the oil level within bearing seal 22 was raised by oneinch to a total height of approximately 2% inches, i.e., a levelapproximately 66 percent higher than conventionally utilized oil levelsfor guide bearings, the leakage rate of inert gas through the sealduring operation was reduced to below approximately 4 cubic feet perhour.

Because an excessive build-up of inert gas pressure within the motorduring operation can drive the oil from lower bearing seal 22 over oilsleeve 46 leading to destruction of the bearing, a pressure releasevalve should be provided within the motor. A particularly preferredpressure release valve in accordance with this invention is illustratedin FIG. 3 and generally consists of a generally Ushaped tube 78 which isfilled with a liquid, such as draft gage fluid 80 (i.e., a commerciallyavailable oil having a density equal to the density of water), to blockescape of inert gas from the motor. The tube, however, preferably isdimensioned so that all the draft gage fluid will be exhausted from theU-shaped tube by an increase in gas pressure within the motor housingbefore oil from the lower bearing seal is forced over oil sleeve 46. Toaccomplish this, the height H of overflow side 82 of U-shaped tube 78should be less than w extends through the motor housing at a locationbelow the heat exchange unit either at the lowest point in the motor ora suitable liquid collecting means, such as sheet metal ducting (notshown), is provided within the motor to channel any water from the heatexchange unit into U-shaped tube 78. Any excessive leakage from the heatexchange unit then overflows from the U-shaped tube to a collectionbasin for disposal.

An alternate seal arrangement permitting conventional levels oflubricant within the lower bearing seal is illustrated in FIG. 4. Thisseal is similar to that illustrated in H6. 2 except an annular plate 81is disposed between the axially lower end of ball bearing nut 58a andthe surface of the oil within oil channel 400 to inhibit oil turbulenceproduced by the ball bearing during rotor rotation from breaking theseal. A substantially enlarged aperture 83, or a plurality of apertures(not shown), then is utilized to communicate oil storage reservoir 42awith bearing oil channel 40a to continuously maintain a full head of oilin lower region 84 of oil channel 40a adjacent the end of the locknutwhile oil flow to bearing 24a is regulated by selectively dimensionedapertures 86 in the plate 81. By partitioning the bearing from the endof the shaft, conventional oil levels can be utilized in the machine.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. ln a dynamoelectric machine characterized by a rotor mounted upon avertically extending shaft, a stator circumferentially mounted aroundsaid rotor, and means for circulating a pressurized fluid through atleast a portion of said machine to remove heat by forced convection andconduction from said pressurized fluid to a cooler surface lying withinthe flow path of said fluid, the improvement comprising a shaft sealsituated between said pressurized fluid and the machine ambient toinhibit excessive leakage of pressurized fluid from said machine, saidseal including a reservoir of liquid lubricant, a bearing disposedcircumferentially about said shaft to permit rotation of said rotorwithin said stator, at least a portion of said bearing being submergedwithin said liquid lubricant, a rotary sleeve fixedly secured to saidshaft to rotate therewith, an axial portion of said sleeve being spacedfrom said shaft to provide an annular zone between said shaft and saidsleeve, a lubricant sleeve extending into the zone between saidrotarysleeve and said rotary shaft, the radially outer face of saidlubricant sleeve serving to confine liquid lubricant within saidmachine, said lubricant sleeve extending axially to a height in excessof the depth of lubricant within said reservoir by an amount at leastequal to the difference in lubricant levels respectively in said annularzone and in said reservoir that are produced by the pressure of saidfluid within said machine, thereby to permit the lubricant level withinthe region between the lubricant sleeve and the rotary sleeve tosubstantially exceed the height of lubricant within said reservoirwithout spilling over said lubricant sleeve, said lubricant within saidbearing seal contacting both said machine ambient and said pressurizedfluid to seal the interior of said machine.

2. A dynamoelectric machine according to claim 1 further including meansfor inhibiting turbulence produced by rotor rotation from penetratingthe region at the lower end of said shaft sleeve to breach said sealduring operation of said machine.

3. A dynamoelectric machine according to claim 2 wherein said turbulenceinhibiting means includes a level of lubricant within said bearing sealin excess of the height of said bearing to completely submerge saidhearing within said lubricant reservoir.

4. A dynamoelectric machine according to claim 3 further including atleast one annular groove notched along the radially outer surface ofsaid shaft sleeve, a bearing cover circumferentially disposed about saidrotary sleeve at an axial location above said bearing seal, said bearingcover having a notch in registration with the groove of said shaftsleeve and means for gravitationally returning lubricant from said notchto said liquid lubricant reservoir.

5. A dynamoelectric machine according to claim 2 wherein said turbulenceinhibiting means includes a selectively apertured annular plate disposedbetween the lower end of said rotary sleeve and said bearing.

6. A dynamoelectric machine according to claim 1 further including acurved tube extending through the housing of said machine, said tubecontaining liquid in communication with both the pressurized fluidwithin said machine and the external environment of said machine, saidtube being dimensioned to be completely exhausted by an increase in thepressure of said pressurized fluid before lubricant is driven over saidoil sleeve within said machine.

7. A vertical dynamoelectric machine comprising a stator, a rotorsecured upon a vertically extending shaft, bearing meansmounted atspaced apart locations along said rotor to permit rotation of said rotorwithin said stator, a housing enclosing said machine, a pressurized heattransfer fluid circulating within said housing to transfer heat absorbedfrom said rotor and stator to a relatively cooler surface along theinterior of said machine, a lower bearing seal situated between saidpressurized fluid and the motor environment to inhibit leakage of saidpressurized fluid from said machine, said seal including a reservoir ofliquid lubricant extending to a height at least partially submerging thelower one of said bearing means, a rotary sleeve fixedly secured to saidshaft at an axially upper portion of said sleeve, said sleeve beingspaced from said shaft along the axially lower portion of said sleeve toprovide an annular zone therebetween, a lubricant sleeve extending intothe annular zone between said shaft sleeve and said shaft, the radiallyouter face of said lubricant sleeve serving as a retaining wall for saidliquid lubricant, said lubricant sleeve extending to a height at least 3inches higher than the level of liquid lubricant within said lowerbearing means to inhibit spillage of said lubricant over said lubricantsleeve, said lubricant within said bearing seal contacting both saidmachine ambient and said pressurized fluid.

8. A vertical dynamoelectric machine according to claim 7 wherein saidpressurized fluid is cooled by heat exchange with liquid pumped throughcoils within said machine, said machine further including a curved tubeextending through the housing of said machine, said curved tubecontaining a liquid in communication with both said pressurized fluidand the outside environment, said tube being dimensioned to becompletely exhausted by an increase in pressure in said machine beforelubricant is driven over said lubricant sleeve.

9. A dynamoelectric machine according to claim 8 wherein said U-shapedtube is situated at a location to receive leakage from said coils, saidtube serving to exhaust liquid in excess of a predetermined amount.

10. A dynamoelectric machine according to claim 7 further includingmeans for inhibiting turbulence prothe upper edges of said lowerbearings.

1. In a dynamoelectric machine characterized by a rotor mounted upon avertically extending shaft, a stator circumferentially mounted aroundsaid rotor, and means for circulating a pressurized fluid through atleast a portion of said machine to remove heat by forced convection andconduction from said pressurized fluid to a cooler surface lying withinthe flow path of said fluid, the improvement comprising a shaft sealsituated between said pressurized fluid and the machine ambient toinhibit excessive leakage of pressurized fluid from said machine, saidseal including a reservoir of liquid lubricant, a bearing disposedcircumferentially about said shaft to permit rotation of said rotorwithin said stator, at least a portion of said bearing being submergedwithin said liquid lubricant, a rotary sleeve fixedly secured to saidshaft to rotate therewith, an axial portion of said sleeve being spacedfrom said shaft to provide an annular zone between said shaft and saidsleeve, a lubricant sleeve extending into the zone between said rotarysleeve and said rotary shaft, the radially outer face of said lubricantsleeve serving to confine liquid lubricant within said machine, saidlubricant sleeve extending axially to a height in excess of the depth oflubricant within said reservoir by an amount at least equal to thedifference in lubricant levels respectively in said annular zone and insaid reservoir that are produced by the pressure of said fluid withinsaid machine, thereby to permit the lubricant level within the regionbetween the lubricant sleeve and the rotary sleeve to substantiallyexceed the height of lubricant within said reservoir without spillingover said lubricant sleeve, said lubricant within said bearing sealcontacting both said machine ambient and said pressurized fluid to sealthe interior of said machine.
 2. A dynamoelectric machine according toclaim 1 further including means for inhibiting turbulence produced byrotor rotation from penetrating the region at the lower end of saidshaft sleeve to breach said seal during operation of said machine.
 3. Adynamoelectric machine according to claim 2 wherein said turbulenceinhibiting means includes a level of lubricant within said bearing sealin excess of the height of said bearing to completely submerge saidbearing within said lubricant reservoir.
 4. A dynamoelectric machineaccording to claim 3 further including at least one annular groovenotched along the radially outer surface of said shaft sleeve, a Bearingcover circumferentially disposed about said rotary sleeve at an axiallocation above said bearing seal, said bearing cover having a notch inregistration with the groove of said shaft sleeve and means forgravitationally returning lubricant from said notch to said liquidlubricant reservoir.
 5. A dynamoelectric machine according to claim 2wherein said turbulence inhibiting means includes a selectivelyapertured annular plate disposed between the lower end of said rotarysleeve and said bearing.
 6. A dynamoelectric machine according to claim1 further including a curved tube extending through the housing of saidmachine, said tube containing liquid in communication with both thepressurized fluid within said machine and the external environment ofsaid machine, said tube being dimensioned to be completely exhausted byan increase in the pressure of said pressurized fluid before lubricantis driven over said oil sleeve within said machine.
 7. A verticaldynamoelectric machine comprising a stator, a rotor secured upon avertically extending shaft, bearing means mounted at spaced apartlocations along said rotor to permit rotation of said rotor within saidstator, a housing enclosing said machine, a pressurized heat transferfluid circulating within said housing to transfer heat absorbed fromsaid rotor and stator to a relatively cooler surface along the interiorof said machine, a lower bearing seal situated between said pressurizedfluid and the motor environment to inhibit leakage of said pressurizedfluid from said machine, said seal including a reservoir of liquidlubricant extending to a height at least partially submerging the lowerone of said bearing means, a rotary sleeve fixedly secured to said shaftat an axially upper portion of said sleeve, said sleeve being spacedfrom said shaft along the axially lower portion of said sleeve toprovide an annular zone therebetween, a lubricant sleeve extending intothe annular zone between said shaft sleeve and said shaft, the radiallyouter face of said lubricant sleeve serving as a retaining wall for saidliquid lubricant, said lubricant sleeve extending to a height at least 3inches higher than the level of liquid lubricant within said lowerbearing means to inhibit spillage of said lubricant over said lubricantsleeve, said lubricant within said bearing seal contacting both saidmachine ambient and said pressurized fluid.
 8. A vertical dynamoelectricmachine according to claim 7 wherein said pressurized fluid is cooled byheat exchange with liquid pumped through coils within said machine, saidmachine further including a curved tube extending through the housing ofsaid machine, said curved tube containing a liquid in communication withboth said pressurized fluid and the outside environment, said tube beingdimensioned to be completely exhausted by an increase in pressure insaid machine before lubricant is driven over said lubricant sleeve.
 9. Adynamoelectric machine according to claim 8 wherein said U-shaped tubeis situated at a location to receive leakage from said coils, said tubeserving to exhaust liquid in excess of a predetermined amount.
 10. Adynamoelectric machine according to claim 7 further including means forinhibiting turbulence produced by rotor rotation from penetrating theregion at the lower end of said shaft sleeve to breach said seal duringoperation of said machine.
 11. A dynamoelectric machine as defined inclaim 7 wherein said lower bearing is completely submerged in saidliquid lubricant.
 12. An invention as defined in claim 11 wherein saidliquid lubricant extends to a height at least 1 inch above the upperedges of said lower bearings.